#include<cstdio>
#include<queue>
#include<algorithm>
using namespace std;

struct nod{int d,c;} a[100005];

priority_queue <int> h;

long long sol,n,x,l,dist,i;

inline bool cmp (const nod &a,const nod &b)
{if(a.d<b.d) return 1; return 0;}

int main ()
{
	freopen("lupu.in","r",stdin);
	freopen("lupu.out","w",stdout);
	scanf("%lld %lld %lld",&n,&x,&l);
	for(i=1;i<=n;i++)
		scanf("%d %d",&a[i].d,&a[i].c);
	sort(a+1,a+n+1,cmp);
	
	for(dist=0,i=1;dist<=x&&i<=n;dist+=l)
		{
			for(;i<=n&&a[i].d<=dist;i++)	 
				h.push(a[i].c);
			if(h.size())
				 {sol+=h.top();
			      h.pop();}
		}
	
				 
	
printf("%lld",sol);

return 0;}